IDEO, a design company, has designed five social mobiles to provoke discussions about the social impact of mobile phones. These are not meant as products, although working models have been built.

1. This phone delivers a variable level of electric shock depending on how loudly the person at the other end is speaking. As a result the two parties are induced to speak more quietly.
   
   
2. This phone allows the user to converse silently: a person receiving a call in a quiet space can respond without speaking, using simple but expressive sounds that they produce and intone manually.
   
   
3. This phone requires the user to play the tune of the phone number they wish to call. The public performance that dialing demands acts as a litmus test of when it is appropriate to make a call.
   
   
4. This user knocks on this phone to communicate the urgency of their call. The recipient hears this knock through their phone and can be discerning about which calls they answer.
   
   
5. This phone can be used to launch sounds into other people's phone conversations. This provides a direct yet discreet way of invading their space.

I find this interesting because of a) the social impact of gaming in public, b) bizarre user interfaces. I especially like the monosyllabic grunts.